Dilation and Superposition...

Illustration of a molecule in the presence of gravitational time dilation. The molecule is in a quantum superposition of being in several places at the same time, but time dilation destroys this quantum phenomenon. (Courtesy: Igor Pikovski, Harvard-Smithsonian Center for Astrophysics)

Topics: Modern Physics, Quantum Mechanics, Schrödinger Wave Equation, Superposition

Why do we not see everyday objects in quantum superpositions? The answer to that long-standing question may partly lie with gravity. So says a group of physicists in Austria, which has shown theoretically that a feature of Einstein's general relativity, known as time dilation, can render quantum states classical. The researchers say that even the Earth's puny gravitational field may be strong enough for the effect to be measurable in a laboratory within a few years.

Our daily experience suggests that there exists a fundamental boundary between the quantum and classical worlds. One way that physicists explain the transition between the two, is to say that quantum superposition states simply break down when a system exceeds a certain size or level of complexity – its wavefunction is said to "collapse" and the system becomes "decoherent."

An alternative explanation, in which quantum mechanics holds sway at all scales, posits that interactions with the environment bring different elements of an object's wavefunction out of phase, such that they no longer interfere with one another. Larger objects are subject to this decoherence more quickly than smaller ones because they have more constituent particles and, therefore, more complex wavefunctions.

Physics World: Does time dilation destroy quantum superposition?
Edwin Cartlidge, science writer in Rome

Quantum Octave...

Image Source: Technology Review

Topics: Hilbert Space, Modern Physics, Quantum Mechanics, Superposition

Curiouser and curiouser! Alice in Wonderland, Chapter 2: The Pool of Tears

TECHNOLOGY REVIEW: One of the features of 20th century art is its increasing level of abstraction from cubism and surrealism in the early years to abstract expressionism and mathematical photography later. So an interesting question is what further abstractions can we look forward to in the 21st century?

Today we get an answer thanks to the work of Karl Svozil, a theoretical physicist at the University of Technology in Vienna and his pal Volkmar Putz. These guys have mapped out a way of representing music using the strange features of quantum theory. The resulting art is the quantum equivalent of music and demonstrates many of the bizarre properties of the quantum world.

Svozil and Putz begin by discussing just how it might be possible to represent a note or octave of notes in quantum form and by developing the mathematical tools for handling quantum music.

They begin by thinking of the seven notes in a quantum octave as independent events whose probabilities add up to one. In this scenario, quantum music can be represented by a mathematical structure known as a seven-dimensional Hilbert space.

A pure quantum musical state would then be made up of a linear combination of the seven notes with a specific probability associated with each. And a quantum melody would be the evolution of such a state over time.

An audience listening to such a melody would have a bizarre experience. In the classical world, every member of the audience hears the same sequence of notes. But when a quantum musical state is observed, it can collapse into any one of the notes that make it up. The note that is formed is entirely random but the probability that it occurs depends on the precise linear makeup of the state.

And since this process is random for all observer, the resulting note will not be the same for each member of the audience.

Abstract:

We consider ways of conceptualizing, rendering and perceiving quantum music, and quantum art in general. Thereby we give particular emphasis to its non-classical aspects, such as coherent superposition and entanglement.

Physics arXiv: Quantum music
Volkmar Putz, Karl Svozil